National Debt, Elvis’s Urge Push Punster Roach on Quest

Sometime before Mary Roach’s new book got the title “Gulp,” I like to think that’s what her editor did in mock, cartoonish panic on hearing that the author planned to dive into the human digestive system.

Letting this brilliantly mischievous writer, for whom no pun is ouch and no cow sacred, dip her pen into the font of all potty humor must have seemed even riskier than her previous excursions into corpses (“Stiff”), the afterlife (“Spook”), sex (“Bonk”) and outer space (“Packing for Mars”).